The principal long-range objective of the proposed research program is to synthesize artificial oxygen-carrying metal complexes which could be utilized as oxygen-supplying agents for physiological systems. The utility of such compounds could range from their application in mechanical oxygenators (artificial lungs) to supplementing the function of hemoglobin (heart disease, asphyxiation). The proposed work is based on the author's discovery of a unique synthetic oxygen-carrying system and a subsequent development of a hypothesis for the reversible oxygenation of metal complexes. The approach to the ultimate goal of the project consists of two interrelated programs: (1) a study of the fundamental aspects of the oxygen-carrying phenomenon, embracing the preparation of new metal complexes and a detailed investigation of (a) the dynamics of their reactions with molecular oxygen and (b) the correlations involving their reactivity, spectra and structures; (2) a utilization of the knowledge emerging from (1) for the synthesis of new oxygen-carrying systems with desired properties.